Mercury vapor generator



May 2, 1961 E. A. BROOKS ETA]. 2,982,269

MERCURY VAPOR GENERATOR Filed Sept. '7, 1955 2 Sheets-Sheet 1 FIG.1

JOHN F HARVEY v JUSTIN F! WINKIN N GEORGE E FRIESE ERNEST A. BROOKS INVENTORS ATTORNEY May 2, 1961 E. A. BROOKS ET AL MERCURY VAPOR GENERATOR 2 Sheets-Sheet 2 Filed Sept. 7, 1955 Q "FIG.3

ATTORNEY United States Patent MERCURY VAPOR GENERATOR Ernest A. Brooks and George F. Friese, Barber-ton, and John F. Harvey, Akron, Ohio, and Justin P. Winkin, Fair Lawn, N.J., assignors to The Babcock & Wilcox fompany, New York, N.Y., a corporation of New ersey Filed Sept. 7, 1955, Ser. No. 532,828

2 Claims. (Cl. 122-510) The present invention relates to vapor generators and more particularly to a mercury vapor generator of relatively small size suitable for the delivery of process heat. Heretofore mercury vapor generators have been constructed in fairly large sizes for power generation purposes and mercury hasnot been used extensively as a heating medium for process purposes where the vapor generating capacity of the mercury generator is relatively small. In all mercury vapor generators problems arise in connection with the characteristics of the mercury. Mercury weighs roughly 13 times as much as water and high temperatures of mercury vapor are attainable at relatively low pressures as compared with steam. The low pressure high temperatures generation of mercury vapor is economically attractive particularly when the heat exchange medium is transmitted through long runs of piping.

In accordance with the present invention a mercury vapor generator is constructed with novel means for compensating for and directing the expansion and contraction of the mercury vapor generating tubes which are heated by gases of combustion. The expansion and contraction of the tubes is guided and directed by a linkage mechanism which permits necessary movement of the parts without the imposition of excessive strains on the metal of the tubes.

The various features of novelty which characterize our invention are pointed out with particularity in'the claims annexed to and forming a part, of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described a preferred embodiment of the invention.

0f the drawings:

Fig. 1 is an elevation, in section, of a mercury vapor generator constructed and, arranged in accordance with the invention;

Fig. 2 is an enlarged elevation of part of the apparatus shown in Fig. 1;

Fig. 2A is a section taken on the line 2A2A of Fig. 2; and

Fig. 3 is a further enlarged section showing another portion of the apparatus shown in Fig. 1.

In the illustrated embodiment of the invention a mercury'vapor generator is arranged to receive the hot products of combustion generated in a refractory lined furnace 11. As shown in Fig. l, the refractory furnace 11 is of generally rectangular horizontal and vertical crosss'ection and is provided with a conventional fluent fuel burner 12 positioned in an end wall 13 of the furnace. The combustion gas temperatures produced in the furnace are regulated by the use of excess air or recirculated flue gases to limit the temperature of the gases leaving the furnace to a value of the order of 2000 F. Such a temperature limitation protects the refractory walls of the furnace and limits the temperature differential between the gases and the mercury'heating surfaces for the protection of the latter. The products of combustion produced in the for- Patented May 2, 1961 flow distribution transversely of the furnace. The prodnets of combustion pass through the openings 14 and pass upwardly through a refractory lined upwardly elongated gas passageway 16 to discharge through a plurality of openings 17 formed in the upper rear wall 18 of the upright passageway. Leaving the upwardly elongated passageway 16 the gases of combustion enter the refractory lined convection pass 20 through which a plurality of rows of mercury vapor generating tubes 21 extend. The hot combustion gases are moved over a spaced series of baffles 28 in generally downward direction through a sinuous flow path toward a gas outlet 22 positioned in the lower portion of the rear wall 23 of the convection pass 20 of the unit; Thereafter the gases are directed in a horizontal direction through a refractory lined flue 24 to discharge upwardly into a stack or a heat trap such as a waste heat boiler, an air heater 25 or the like.

As disclosed and claimed in a co-pending application Serial No. 53 ,826, filed September 7, 1955 now Patent No. 2,890,684 in the name ofJustin P. Winkin one of the co-inventors of this application, the gases of combustion leaving the air heater 25 may be passed to a waste heat boiler (not shown) for further heat recovery. Alternately the gases of combustion can be discharged to the atmosphere, if so desired. Due to the high temperature of the mercury vapor generated in the convection tubes 21, the gases of combustion leaving the mercury vapor generator are ordinarily of a high order and the temperature of the gases leaving the air heater retain sufiicient heat in some cases to justify the installation of a waste heat boiler in the flow path of the gases of combustion.

As hereinafter described the bafiles positioned in the convection pass of the vapor generator are constructed of steel and refractory materials and are so positioned as to cause the gases to pass serially across the heat exchange surfaces of the mercury vapor tubes.- With the high temperatures involved in the generation of mercury vapor the expansion and contraction of the tubes 21 in the oonvec-.

tion bank 20 is appreciable. Accordingly, the tubes are arranged for guided expansion and contraction so as to minimize the strains imposed upon the parts of the circulatory system of the mercury vapor generator 10.

As shown particularly in Figs. 1 and 2 the tubes 21 are attached to the lower segment of an upper drum 26 which is supported on the structural steel 27 of the unit. The tubes 21 are substantially upright through a major portion of their upper sections and in the embodiment shown, are arranged inrows of four tubes positioned transverse to the horizontally disposed longitudinal axis of the drum I 26. The tubes are upright through a major portion of their extent, and are curved in their lower end portions to open into a pair of horizontally disposed inletheaders 30 and 31. Each of the headers 30 and 31 receive two of the tubes 21 of each tube row, and each header is provided with a branch connection 32 and 33, respectively, from a downcomer 34 on each side of the refractory setting of the vapor generator. As shown, the downcomer 34 andbranch 32 are inclined and extend from the lower header 30 to the lower end portion of the drum, while the branch connection 33 to the lower header 31 is provided with an offset bend which opens to the downcomer 34. The intermediate length portion 35 of the downcomer 34 has a cross-sectional area somewhat greater than the sum of the two branch connections 32 and 33 to the lower headers. The upper end portion 36 of the downcomer 34 is enlarged to a cross-sectional area of the order of six times the cross-sectional area of the intermediate portion 35 of the downcomer. In operation the mercury liquid level in the unit is maintained in the enlarged cross-sectional area portion 36 of the upper end of the downcomer 34. According to good operating practice the upper downcomer portion is provided with a plurality of plates 37 (see Fig. 2) positioned parallel to the axis of the downcomer to serve as vortex inhibiters.

As shown in Figs. 1 and 2 the lower headers are maintained in positional relationship by a pivoted linkage which includes stub plate members 40 and 41 welded to the headers 30 and 31, respectively, with a connecting arm 42 member pivotally attached to each. The header 31 is provided with a plate member 43 Welded to the surface thereof, Which in turn is pivotally attached to a rod 44 of adjustable length pivotally fixed to a flange member 45 welded to the structural steel 46 supporting the generating unit 10. The rod 44 is provided with a turn buckle 47 to provide means for adjusting the length of the rod with the entire assembly of linkage connections between the horizontally disposed headers 30 and 31 and the structural steel 46 positioned on opposite sides of the refractory setting of vapor generating unit so as to be out of the path of the hot gases of combustion produced in the furnace.

In operation the downcomer 34 and the lower headers 30 and 31 contain liquid mercury which will be, particularly during starting-up periods or during changes in the operating rate of the unit, at a lower temperature than the vapor generating or riser tubes 21 of assembly. The gases of combustion passing over the convection heated tubes 21 of the vapor generator will heat the tubes which will expand in a downward direction from their fixed position at the drum 26 of the unit. With the downcomers located on the exterior of the gas-pass, thermal expansion will occur only by reason of hot mercury liquid passing therethrough. Thus the tubes, having a greater change oftemperatures, will have a greater lineal expansion than the downcomers. Under these conditions the headers 30 and 31 will move in a generally downward and outward direction, in response to the expansion of the assembly, as guided and restrained by the guiding linkage including the rod 44 positioned on the exterior sides of the unit setting.

As hereinbefore referred to, the bafile members in the convection gas pass of the unit are each constructed of flanged steel plate members 50 supporting refractory material 51 positioned on the upper side of the plates 50. The bafiie plates are horizontally disposed and are maintained in position relative to the tubes 21 by metallic blocks 52 welded to the outermost tube in each row. The plate 50 and refractory material 51 on the upper side of each of the baffles 28 are provided with openings therethrough for the upwardly extending tubes. The blocks 52 support the baffles 28 to maintain the Vertical relationship between tubes 21 and each baffle 28 substantially constant while the transverse spacing of the tubes is maintained substantially uniform by the bafile plates 50.

The lowermost baffle 53 is provided with a linkage attached to the refractory wall 18 of the convection gas pass 20. This construction is shown in Fig. 3 where the linkage consists of a horizontally disposed channel member 54 embedded in the wall 18 and an upwardly extending flange member 55 which is welded thereto. A rod 56 is horizontally extended through the wall 18 to the flange 55 to form an anchor for the baffle supporting linkage. The outer end of the rod 56 is threaded to a nut 57 and washer resting against the wall 18 in the elongated gas pass 16. The inner end of the rod 56 is provided with a plate 58 which is welded to the end of the rod and pivotally attached to a linkage arm 60. The opposite end of the linkage arm 60 is in turn pivotally attached to a vertically extending flange of the baffle plate member 50. With this construction, the horizontal alignment and upright relationship of the vapor generating tubes 21 is 4. maintained above the lowermost baffle 53 throughout the operating temperature changes of the tubes.

With the baflles 28 and 53 supported upon the tubes 21, the bafiles will move with the tubes in a vertical direction relative to the refractory wall 18 of the convection gas pass 20. So as to maintain an operative arrangement of the baffles, a fixed ledge 61 is built out from the wall 18 into the convection gas pass 20 to a position adjacent the end of each of the bafiles. A refractory tile member 62 is laid over the joint between the fixed refractory shelves 61 of the convection pass and the adjacent baffie. Thus, as the bafiles 28 and 53 move in a vertical direction relative to the shelves 61 the tile members 62 will tilt, and effectively maintain the relatively moving baflles in an effective condition.

The mercury vapor generated in the tubes 21 in the convection gas pass 20 discharges upwardly through the tubes into the drum 26. The tubes are each provided with a reverse bend tubular element 63 or a tube bend which is welded to the upper end of the tube within the drum. Thus, the ascending mixture of mercury liquid and vapor entering the drum 26 is projected downwardly by the reverse bend tubes 63 for separation of vapor from the liquid with the latter entering the downcomers 35.

The mercury vapor delivered to the heat users (not shown) is delivered as condensate to the drum 26 through a return line 87, and discharged into the channel 83. The incoming mercury liquid thus enters the circulatory system of the vapor generator to mix with the liquid therein.

In one embodiment of illustrated invention a mercury vapor generator had a capacity of 3,000,000 B.t.u. per hour. This capacity was attained with a vapor heating surface consisting of 84% ID tubes arranged in 4 rows of 21 tubes per row, and with heat supplied by the combustion of natural gas. Recirculation of flue gases at a temperature of about 580 F was used to limit the heating gas temperature to approximately 2,000 F., leaving the furnace 11. Mercury vapor was delivered from the drum 26 at a pressure of approximately 66 p.s.i.a. and a temperature of about 850 F.

While in accordance with the provisions of the statutes we have illustrated and described herein a preferred embodiment of the invention, those skilled in the art will understand that changes may be made in the method of operation and form of the apparatus disclosed without departing from the spirit of the invention covered by our claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

1. A mercury vapor generator comprising a horizontally disposed upper drum, a header located below said upper drum with the longitudinal axis thereof parallel to the longitudinal axis of and outwardly displaced out of vertical alignment with said drum, an external downcomer connecting each end portion of said header with said upper drum, a plurality of vapor generating tubes having the upper portions thereof positioned in upright planes and their lower portions outwardly curved to connect with said header, means for heating said tubes, means intermediate the length of said tubes for maintaining the upright portions of said tubes in vertical alignment with said upper drum during thermal movement of the tubes, and a rod pivotally attached at one end to said header and having its opposite end pivotally secured to a fixed member spaced horizontally from the upright axes of said tubes for guiding the movement of said header during thermal movements of the lower curved portions of said connecting tubes and said downwcomers in a downward and outward arc.

2. A mercury vapor generator comprising a horizontally disposed upper drum, horizontally disposed headers located below said upper drum with the longitudinal axes thereof parallel to the longitudinal axis of and displaced out of vertical alignment with said drum, a downcomer connecting each end of said headers with said upper drum, a plurality of vapor generating tubes connecting said headers with said upper drum, means for heating 1 said tubes, said tubes having the upper portions thereof positioned in upright planes and their lower portions curved to connect with said header, means for maintaining the upright portions of said tubes in alignment with said upper drum during thermal movement of the-tubes, and means for guiding the movement of said headers during thermal movements of the connecting tubes including pivotal connections between said headers, and a rod pivotally attached at one end to one of said headers and having its opposite end pivotally secured to a fixed member spaced horizontally from the upright axes of said tubes.

References Cited in the file of this patent UNITED STATES PATENTS Jacobus Aug. 19, Kestner June 25, Pratt Feb. 16, Bell Apr. 5, Wright May 24, Emmet Jan. 14, Andrews June 23, Emmet -2. July 27, Fletcher Jan. 30, Loughin et al Mar. 23, Lloyd Dec. 21, Frisch Jan. 25,

FOREIGN PATENTS Germany July 4, Switzerland Jan. 2, 

